In general, activated sludge treatment has been conducted for treatment of organic compounds in industrial wastewater. In recent years, however, compounds that can not be degraded by conventional activated sludge treatment, for example, hardly biodegradable chelating agents including EDTA, organic chlorine compounds including trihalomethanes, and various surfactants of nonyl phenol derivatives, are discharged into nature, which presents a social problem from fear of environmental pollution and an increased burden on the environment. It is difficult to biodegrade these compounds by the conventional activated sludge process, and particularly, when the compounds exist at a high concentration (for example, 200 ppm or more), the adverse effect thereof is profound.
For example, the above-mentioned hardly biodegradable chelating agents are generally used in industrial soap, the photographic industry, the pulp industry and the plating industry. Wastewater containing such hardly biodegradable materials has a high COD value. However, such materials are not degraded by the conventional activated sludge treatment. Accordingly, as a method for treating the wastewater, a dilution method of reducing the concentration of the materials to an effluent control value or less by diluting the wastewater with different water has most generally been used.
In addition, recovery incineration treatment has also been used in some cases.
However, in the dilution method, the cost of water is high, and the total amount of the hardly biodegradable material discharged is not decreased. Further, in the recovery incineration method, the burden of the treating cost is further increased.
For this reason, a treating method of degrading the hardly biodegradable material with a microorganism has been developed, as a wastewater treating method low in the treating cost and essentially decreasing the total amount of the hardly biodegradable material contained. However, in such a treating method, it is difficult to control the microorganism. In particular, when a plurality of treatment tanks are installed, it is necessary to control activity of the microorganism in each tank. It becomes therefore necessary to control the wastewater treatment by an expert. However, it is actually difficult to independently conduct it by each factory unit.
In addition, when the treatment is conducted by mixing a particular microorganism that can degrade the hardly biodegradable compound in a conventional activated sludge tank, it is very difficult to control conditions under which both the microorganism already existing in the activated sludge tank and the particular microorganism newly introduced therein are brought into action. In general, the existing microorganism becomes predominant, and activity of the latter microorganism is lowered in many cases. Accordingly, in such a mixed system, it is necessary to control the conditions for sustaining activity of each microorganism. It becomes therefore necessary to control the wastewater treatment by an expert. However, it is actually difficult to independently conduct it by each factory unit.
Further, in the field of business relating to degradation of hardly biodegradable compounds with microorganisms, rewards have hitherto been reaped by selling the microorganisms. However, the microorganisms are easily proliferated under specific conditions. Accordingly, once the microorganisms are sold, it becomes unnecessary that the purchasers buy them again. The problem is therefore encountered that the wastewater treatment business utilizing such microorganisms for wastewater treatment is not feasible as business. It is therefore a reality that a positive search of the microorganisms for this purpose has not been conducted.